A high performance backscattering set-up using multimode light channels

The utilization of multimode ion-exchanged waveguides to form an optical directional coupler for multimode fibre backscattering measurements is discussed. The optical properties of the integrated branching element are described in detail. A very high directivity of 70 dB was obtained with this new device. The dynamic range in the backscattering measurement was 23 dB fibre one-way loss.     

Optical transmission of bulk plastic material and plastic lightguides at high optical powers

Optical transmission measurements were performed with bulk plastic materials and plastic fibres regarding the possible application as a transmission media for high optical powers. Transmission losses of PMMA bulk material and PS/PMMA core-cladding combination optical fibres were determined to be 0.757 dB m^-1 and 1.41 dB m^-1 at 514.5 nm, respectively. The core material of the investigated fibres withstands a power density of 3.8 x 10³ W mm^-2 when the light is suitably launched. With the light source available a transmitted cw output power of 2.1 W could be attained with a 1.5 m long fibre.     

Improving performance of optical fibre chaotic communication by dispersion compensation techniques

This paper numerically investigates the effects of dispersion on optical fibre chaotic communication, and proposes a dispersion compensation scheme to improve the performance of optical fibre chaotic communication system. The obtained results show that the transmitter-receiver synchronization progressively degrades and the signal-to-noise ratio of the recovered message deteriorates as the fibre length increases due to the dispersion accumulation. Two segments of 2.5-km dispersion-compensating fibres are symmetrically placed at both ends of a segment of 245-km nonzero dispersionshifted fibre with low dispersion in one compensation period. The numerical results show that the signal-to-noise ratio of the extracted 1 GHz sinusoidal message is improved from -2.92 dB to 15.38 dB by this dispersion compensation for the transmission distance of 500 km.     

Near-noiseless amplification of light by a phase-sensitive fibre amplifier

We report near-noiseless (noise figure of 0.4 dB, which is an improvement over the theoretical limit of 1.2 dB for a conventional laser amplifier with the same gain of 1.7 dB) optical amplification of laser light in a phase-sensitive fibre amplifier.     

Study of in-line single-mode optical fiber polarizer

The theoretical calculation method of multilayer metal-clad planar optical waveguide presented by Y. YAMAMOTO is greatly improved and transplant into the optical fiber and a suitable waveguide model of in-line single-mode optical fiber polarizer is set up to study its characteristics, the theorical analyses are in accordance with the experimental re suits. The polarizer whose extinction ratio is more than 30 dB at 0.633μm wavelength with an insertion loss of 0.5 dB is formed by grinding off the cladding on one side of a single-mode fibre and evaporating metal onto the polished durface in our Lab.     

Improved planar optical branching elements for multimode fibre transmission systems

The optical tapping and fan-out elements which we had previously fabricated for multimode fibre transmission systems all suffered from the serious drawback that the aging of the light-sensitive foil used in our simple planar technology resulted in a deterioration in the performance of structures using such foil as a planar waveguide. This paper introduces improved optical structures in which this drawback has been avoided while stil retaining the simple technique by which high fibre positioning accuracy is assured. In addition the overall insertion loss of the structures has been reduced to about 2 dB for the fan-out structure and 1.2 dB–1.5 dB for the access coupler.     

On the feasibility of optical fibre sensors for strain monitoring in thermoplastic composites under fatigue loading conditions

This study investigates the possibility of using optical fibres with Bragg gratings for measurements in thermoplastic composites under fatigue loading conditions. Two setups are considered: (i) the fibre is embedded in the composite and (ii) the grating is bonded externally. Detailed information is given on the principle of optical fibre measurements and the data acquisition for both setups. To verify the strain derived from the optical fibre, the strain is compared with extensometer measurements. A special design of the blades of the extensometer is presented, since the standard blades suffer from a loss of grip on the surface of the specimen. The material used for this study was a carbon fibre-reinforced polyphenylene sulphide.It can be concluded for both setups that the optical fibre survives over half a million loading cycles, without de-bonding of the fibre. The advantage of the external fibre over the embedded one is that it can be mounted after manufacturing of the plate, but it has a higher risk of being damaged during working conditions of the component.     

基于双折射效应的普通单模光纤频率偏移器和偏振控制器

本文介绍了利用普通单模光导纤维弯曲产生的双折射效应而研制成的频率偏移装置和偏振控制装置.频率偏移装置的单边带抑制达30dB以上,它与光纤偏振控制装置一起是构成全光纤功能型传感器比较理想的光纤元件.     

Hybrid flat gain C-band optical amplifier with Zr-based erbium-doped fiber and semiconductor optical amplifier

An efficient gain-flattened C-band optical amplifier is demonstrated using a hybrid configuration with a Zirconia-based Erbium-doped fibre (Zr-EDF) and a semiconductor optical amplifier (SOA). The amplifier utilizes a two-stage structure with a midway isolator to improve flat gain characteristic and reduce noise figure. At input signal power of −30 dBm, a flat gain of 28 dB is obtained from wavelength region of 1530 to 1560 nm with gain variation of less than 4 dB. The noise figure is maintained below 11 dB at the flat-gain region. This amplifier has the potential to be used in the high channel count dense wavelength division multiplexing system due to its simplicity and compact design.     

基于新型长周期光纤光栅的掺铒光纤放大器

报道了基于高频CO₂激光脉冲写入的新型长周期光纤光栅的低噪音掺铒光纤放大器,这种新型长周期光纤光栅是用大约几千Hz的高频CO₂激光脉冲对光纤玻璃热冲击作用而形成的.在铒纤中插入一个长周期光纤光栅,会明显减少掺铒光纤放大器的放大自发辐射(ASE)噪音.报道了两种低噪音掺铒光纤放大器,作为前置放大器和线路放大器,它们的ASE噪音指数分别从4.0 dB减少到3.5 dB和从4.8 dB减少到4.3 dB,并且在作为线放时,其小信号增益从30 dB提高到37 dB,降噪及提高增益效应十分显著.     

Efficient Fibre Amplifiers Based on a Highly Er3＋/Yb3＋ Codoped Phosphate Glass-Fibre

Highly Er3＋ /yb3＋-codoped single-mode phosphate glass fibre is fabricated by the rod-in-tube technique. The performances of high-concentration Er3＋ /yb3＋-codoped phosphate glass fibre amplifiers are investigated and discussed. An efficient optical fibre amplifier with a gain of 12.6 dB based on a 3.0 cm long Era＋ /ybe＋-codoped phosphate glass fibre is demonstrated under a dual-pump configuration with two 976 nm fibre-pigtail laser diodes, which make it attractive for compact Er3＋-doped fibre amplifiers. The obtedned noise figures of signal wavelength from 1525 to 1565nm are less than 6.0dB. Gain saturation behaviour at 1535nm is also investigated, and the obtained saturation output power is larger than 10 dBm.     

Design of dual-core resonant leaky optical fibre based gain flattening filters for erbium doped fibre amplifiers

We propose optical fibre based filters employing dual-core resonant leaky structure for gain equalization of erbium doped fibre amplifier (EDFA). Spectral loss variation of the structure has been utilized to suppress gain peak and, thus, flatten overall gain profile in the C-band. We show 15.7 dB flat gain with ± 1.6 dB ripple in the wavelength range from 1525 nm to 1555 nm using a single filter and 18±0.7 dB gain using two cascaded filters.     

A Novel Design of Grating Couplers for Efficient Broadband Coupling between Silicon-on-Insulator Nanophotonic Waveguides and Fibres

A novel design of out-of-plane grating couplers is proposed for coupling between silicon-on-insulator nanophotonic waveguides and single-mode fibres. The coupler with the first-order diffraction coupling to the optical fibre is actually a second-order reflected grating with two times of period of the first-order grating. To enhance outcoupled power, a back hole is designed to form in the silicon substrate and a kind of metals is placed on the top acting as a reflection layer. The coupler is optimized using coupled-mode-based simulations, showing that the coupling efficiency to and from tapered optical fibre can be as high as 85% with 1dB bandwidth about 23 nm.     

Stable Dual-Wavelength Fibre Laser with Bragg Gratings Fabricated in a Polarization-Maintaining Erbium-Doped Fibre

A new polarization-independent duai-wavelength fibre laser by fabricating a uniform FBG and a chirped FBG in a polarization-maintaining erbium-doped fibre （PM-EDF） is proposed and demonstrated. The wavelength spacing is 0.18nm and the optical signal-to-noise ratio is greater than 50dB with pump power of 246mW. Chirped FBG is used to make the reflectivity wavelengths of two PM-FBGs match easier. Since both EDF and FBGs are polarization-maintaining without splices and the two wavelengths are polarization-independent, the maximum amplitude variation and wavelength shifts for both lasing wavelength with 3-min intervals over a period of six hours are less than 0.2 dB and 0.005 nm, respectively, which shows stable dual-wavelength output.     

棱镜分光式光学环行器及其应用

本文介绍梭镜分光式光学环行器设计理论与制备工艺以及在光纤通信和光纤传感系统中的应用。所研制的光学环行器光纤-光纤(单模)插入损耗小于2.8dB,隔离比大于25dB,回波损耗优于40dB.器件性能与偏振无关。     

Flat Supercontinuum Generation at 1550 nm in a Dispersion-Flattened Microstructure Fibre Using Picosecond Pulse

The generation of a flat supercontinuum of over 80nm in the 1550nm region by injecting 1.6ps 10 GHz repetition rate optical pulses into an 80-m-long dispersion-flattened microstructure fibre is demonstrated. The fibre has small normal dispersion with a variation smaller than 1.5 （ps·nm^-1·km^-1） between 1500 and 1650nm. The generated supercontinuum ranging from 1513 to 1591 nm has the flatness of ±1.5 dB and it is not so flat in the range of several nanometres around the pump wavelength 1552nm. Numerical simulation is also used to study the effect of optical loss, fibre parameters and pumping conditions on supercontinuum generation in the dispersion-flattened microstructure fibre, and can be used for further optimization to generate flat broad spectra.     

4×10Gb/s 400km 啁啾光纤光栅色散补偿研究

介绍了利用光纤光栅成功实现了4×10Gb/s 400km G-652光纤的色散补偿，各信道传输部分在误码率为10-10时，无误码传输的功率代价均小于2dB，且最好的功率代价为负值- 关键词： 光纤光栅 色散补偿 功率代价     

Multi-Edge-Written Long-Period Fibre Gratings with Low PDL by Using High-Frequency CO2 Laser Pulses

A novel long-period fibre grating （LPFG） with low polarization-dependent loss （PDL） is fabricated by using a multi-edge exposure method with high frequency CO2 laser pulses. The experimental results show that the PDL of a triple-edge-written LPFG with a peak amplitude of-16.5 dB can be as low as 0.22 dB. These hovel LPFGs can find important applications in optical communication and sensing.     

Polymer optical fibre Bragg gratings based fibre laser

For the first time the fibre laser constructed from a polymer optical fibre Bragg grating is reported. The single frequency laser with the peak power of −5 dBm and signal to noise ratio greater than 45 dB has been achieved. Further examination demonstrates the excellent characteristics of the fibre laser. First, the fibre laser can be easily tuned over 35 nm by the simple axial tension method. Second, the fibre laser has the high strain sensitivity of 1.48 pm/με with the dynamic measurement range as large as 2.37%.     

基于SOA和级联取样光纤光栅的多波长激光器

研究了基于半导体光放大器(SOA)和双段级联取样光纤光栅构成的新型结构多波长激光器.设 计了取样光纤光栅，计算了其反射谱，模拟了多波长激光器的输出光谱.基于自行制作的SOA 和取样光纤光栅，进行了多波长激光器的实验研究，得到了间隔为0.8nm、输出功率不平坦 度小于1.0dB的11个波长输出.理论和实验两个方面都可以验证：与基于普通取样光栅的多波 长方案相比，基于双段级联取样光栅的方案能改善输出谱平坦度，并可提高可激射波长数. 关键词： 半导体光放大器 取样光纤光栅 多波长激光器